diagonal pixel differences of image matrix

is there any method to get the diagonal pixel differences(left right diagonal) of a image matrix.for example , i have to obtain [-8 -2 -4;4 2 -16;0 2 4] from [2 1 8 24;9 10 3 12;2 5 8 19;1 2 3 4]

Answer 1

[Andrei Bobrov]

b = [2 1 8 24;9 10 3 12;2 5 8 19;1 2 3 4];

out = rot90(spdiags(tril(triu(flipud(diff(flipud(spdiags(b,-2:2))))),2)));

other variant without spdiags

s = size(b);
c = ones(s + [0 s(1)-1]);
c1 = rot90(tril(triu(c),s(2)-1));
c1(c1>0) = b';
c2 = diff(c1');
c3 = c2(:,end-1:-1:2);
t = tril(triu(ones(size(c3))),s(2)-2);
c3 = rot90(c3);
out = zeros(s-1)';
out(:) = c3(rot90(t)>0);
out = -out';

Answer 2

[Teja Muppirala]

b = [2 1 8 24;9 10 3 12;2 5 8 19;1 2 3 4];

conv2(b,[-1 0; 0 1],'valid')

[Andrei Bobrov]

Hi Teja! +1. I again forgotten about conv.

[Teja Muppirala]

Hello Andrei! conv is simpler, but your solution is definitely more creative and interesting.